EP3069441B1 - Method and system for controlling an automotive vehicle three-phase electric machine supplied via chopped voltages - Google Patents

Description

The invention relates to the technical field control of an electric machine for a motor vehicle, and more particularly the control of torque oscillations of such a machine.

In the development of electric vehicles, the torque provided by the electric motor must be controlled. The torque of a machine being directly related to the currents flowing in it, it must therefore be able to precisely control these currents. The electric motor to be controlled may in particular be a three-phase synchronous machine with wound rotor.

The currents in the three phases of the stator are sinusoidal and each phase shifted by 2π / 3 rad. These currents create a rotating magnetic field in the machine. The rotor is traversed by a direct current which creates a magnetic field which makes it equivalent to a magnet. To achieve the mechanical torque, the stator magnetic field is controlled in quadrature, that is to say in constant controlled phase shift of 90 ° with the rotor field. Thus, the rotation frequency of the rotor field is equal to the frequency of the stator currents, hence the name "synchronous". It is the magnitudes of the stator currents and the value of the rotor current that creates the torque needed for machine rotation. To control these currents, it will therefore be necessary to apply sinusoidal voltages between the phases of the stator, each being also phase shifted by 2π / 3 rad and to apply to the rotor a constant voltage.

On the other hand, the Park transform is used to project the stator currents and voltages into a space where the sinusoidal signals become constants. The Park mark corresponds to a reference linked to the rotating field, thus linked to the rotor in the case of the synchronous machine. The use of the Park transform allows to have to regulate constants, which is much easier to achieve than to regulate sinusoidal signals.

The challenge is to regulate constant currents by controlling constant voltages. By performing the inverse transform, it is possible to reduce to the reference of the stator of the machine and therefore to know precisely the voltages to be applied to each phase of the electric machine.

To regulate the currents in the machine, a corrector is necessary because, it is known that a three-phase machine powered with chopped voltages generates oscillations of torque at certain frequencies corresponding to harmonics of the electrical frequency (rotation frequency of the rotor of the machine).

In the Park space, the system to be controlled is as follows: $$\begin{array}{cc}{\mathrm{V}}_{\mathrm{d}}& ={\mathrm{R}}_{\mathrm{s}}{\mathrm{I}}_{\mathrm{d}}+{\mathrm{The}}_{\mathrm{d}}\stackrel{•}{{\mathrm{I}}_{\mathrm{d}}}+{\mathrm{M}}_{\mathrm{f}}\stackrel{•}{{\mathrm{I}}_{\mathrm{f}}}-{\mathrm{\omega }}_{\mathrm{r}}{\mathrm{The}}_{\mathrm{q}}{\mathrm{I}}_{\mathrm{q}}\hfill \\ {\mathrm{V}}_{\mathrm{q}}& ={\mathrm{R}}_{\mathrm{s}}{\mathrm{I}}_{\mathrm{q}}+{\mathrm{The}}_{\mathrm{q}}\stackrel{•}{{\mathrm{I}}_{\mathrm{q}}}+{\mathrm{\omega }}_{\mathrm{r}}\left({\mathrm{The}}_{\mathrm{d}}{\mathrm{I}}_{\mathrm{d}}+{\mathrm{M}}_{\mathrm{f}}{\mathrm{I}}_{\mathrm{f}}\right)\hfill \\ {\mathrm{V}}_{\mathrm{f}}& ={\mathrm{R}}_{\mathrm{f}}{\mathrm{I}}_{\mathrm{f}}+{\mathrm{The}}_{\mathrm{f}}\stackrel{•}{{\mathrm{I}}_{\mathrm{f}}}+{\mathrm{\alpha M}}_{\mathrm{f}}\stackrel{•}{{\mathrm{I}}_{\mathrm{d}}}\hfill \end{array}$$

• V_d, V_q et V_f : respectivement la tension direct, la tension en quadrature et la tension du rotor (en Volt),
• I_d, I_q et I_f : les courants circulant dans la machine sur les trois axes du plan de Park (en Ampère),
• İ_d, İ_q et İ_f les dérivées des courants respectifs I_d, I_q et I_f,
• R_s et R_f : les résistances du stator et du rotor de la machine (en Ohm),
• L_d, L_q et L_f : les inductances sur chaque axe de la machine (en Henry),
• M_f : l'inductance mutuelle entre le stator et le rotor (en Henry),
• α : un terme constant issu de la transformée de Park (sans unité),
• ω_r : la vitesse de rotation du champ magnétique de la machine (en rad/s),

With:

• V _d , V _q and V _f : respectively the direct voltage, the quadrature voltage and the rotor voltage (in volts),
• I _d , I _q and I _f : the currents circulating in the machine on the three axes of the plan of Park (in Ampere),
• İ _d , İ _q and İ _f the derivatives of the respective currents I _d , I _q and I _f ,
• R _s and R _f : the stator and rotor resistances of the machine (in Ohm),
• L _d , L _q and L _f : the inductances on each axis of the machine (in Henry),
• M _f : the mutual inductance between the stator and the rotor (in Henry),
• α: a constant term resulting from the transform of Park (without unit),
• ω _r : the speed of rotation of the magnetic field of the machine (in rad / s),

It should be noted that, in the case of a synchronous machine, the rotational speed ω _r of the magnetic field of the machine is equal to the speed of rotation of the rotor multiplied by the number of pairs of poles of the machine.

$$-{\mathrm{V}}_{\mathrm{bat}}\le {\mathrm{V}}_{\mathrm{f}}\le {\mathrm{V}}_{\mathrm{bat}}$$

The voltages V _d and V _q are created with an inverter, the voltage V _f is created with a chopper, both systems being powered by a battery. A chopper cuts DC voltages to produce DC voltages of different amplitude with high efficiency. When an inverter and a chopper are used, the following constraints must be respected: $$\sqrt{{\mathrm{V}}_{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}^{\mathrm{2}}+{\mathrm{<figure-callout\; id="2"\; label="V\; q"\; filenames="imgf0001.png"\; state="\{\{state\}\}">V\; </figure-callout>}}_{\mathrm{q}}^{\mathrm{}}}\le \frac{{\mathrm{V}}_{\mathrm{beats}}}{\mathrm{3}}\mathrm{and}$$

$$-{\mathrm{V}}_{\mathrm{beats}}\le {\mathrm{V}}_{\mathrm{f}}\le {\mathrm{V}}_{\mathrm{beats}}$$

With V _bat : the voltage of the battery that powers the inverter and the chopper.

However, such a system has torque oscillations that can cause a divergence of the current regulator.

From the state of the art the following documents are known.

The request for FR2973607 aims to reduce torque oscillations at the source. However, the power is calculated in terms of power to the battery, which generates power losses. In addition, such a calculation requires an additional current sensor to measure the DC current. In addition, the new current setpoints are calculated from the new torque setpoint.

In the document EP 1906523 the torque oscillations are eliminated by applying a voltage V _f across the inductor. There is no description of centralized or decentralized power processing.

The document EP 1944861 does not describe any processing at the power level. Nevertheless, a decentralization of compensation processing is described. In other words, the direct axis d and the axis in quadrature q are treated separately. For this, it is described a real-time calculation of a phase shift between the electric angle of the current and the expected electric angle to compensate for torque oscillations.

It is thus described a form of regulation anticipating current measurements in order to produce voltages that compensate for the oscillatory phenomenon of the torque.

It is also known to apply a correction called "curative anti-knock", in which is applied to the speed measurement of the electric machine a filtering calculated from a dynamic model of the kinematic chain. The signal thus processed represents a torque setpoint out of phase with respect to the torque oscillations. This is injected into the main torque setpoint and achieves oscillation attenuation.

However, these solutions do not reduce the oscillations "at the source", that is to say at the level of the electrical power, and over the entire range of rotational speeds.

There is therefore a need for a control method of an electric motor to reduce the harmonics of torque related to the topology of the machine.

• on détermine les puissances de chaque phase de la machine électrique exprimées dans le repère de Park,
• on détermine si une mesure de la vitesse de rotation du champ magnétique dans la machine électrique dépasse une valeur de seuil, si tel est le cas, on réalise un filtrage passe-bande des puissances de chaque phase de la machine électrique,
• on multiplie chaque puissance après filtrage par des gains calibrables pour obtenir des courants d'atténuation relatifs à chaque phase,
• on détermine des consignes de courant finales en soustrayant les courants d'atténuation relatifs à chaque phase des consignes de courant des phases correspondantes, et
• on détermine des consignes de tension d'alimentation des phases de la machine électrique en fonction des consignes de courant finales.

An object of the invention is a method for controlling a three-phase electric machine of a motor vehicle powered by chopped voltages and comprising a step of determining current setpoints for each phase of the electric machine according to a torque request. of the driver, and a step of determining the voltages of each phase of the electric machine according to the current instructions for each phase. Chopped voltages means voltages coming from a chopper making it possible to modify the amplitude of an input voltage by cutting. The method comprises the following steps in which:

• the powers of each phase of the electric machine expressed in the Park mark are determined,
• determining whether a measurement of the rotational speed of the magnetic field in the electric machine exceeds a threshold value, if this is the case, a band-pass filtering of the powers of each phase of the electric machine is carried out,
• each power is multiplied after filtering by calibrated gains to obtain attenuation currents relative to each phase,
• final current setpoints are determined by subtracting the attenuation currents relative to each phase from the current setpoints of the corresponding phases, and
• phase voltage instructions for the electric machine are determined according to the final current instructions.

The bandpass filtering can be performed for a low cutoff frequency lower than the rotation frequency of the magnetic field at which the oscillations are observed and a high cutoff frequency higher than the rotation frequency of the magnetic field at which the oscillations are observed.

The electric machine can be synchronous or asynchronous.

The rotation speed threshold of the magnetic field is determined as a function of the rotational speed of the magnetic field at which torque oscillations are observed.

Another object of the invention is a control system of a three-phase electric machine of a motor vehicle powered by chopped voltages, comprising means for determining current setpoints of each phase of the electric machine according to a request from torque of the conductor, and a current regulating means adapted to determine voltages of each phase of the electric machine according to the current instructions for each phase. The system comprises a means for correcting the torque oscillations, able to determine the powers of each phase of the electric machine expressed in the Park mark, the correction means also being able to determine whether a measurement of the rotation speed of the field in the electrical machine exceeds a threshold value, and to carry out a band pass filtering of the powers of each phase of the electric machine, and to determining attenuation currents relative to each phase as a function of the powers after filtering, and subtractors able to subtract the attenuation currents relative to each phase from the current orders relative to the corresponding phases in order to obtain final current instructions, and able to transmit the final current instructions to the control means of the electric machine.

The bandpass filtering can be performed for a low cutoff frequency lower than the rotation frequency of the magnetic field at which the oscillations are observed and a high cutoff frequency higher than the rotation frequency of the magnetic field at which the oscillations are observed.

The rotation speed threshold of the magnetic field is determined as a function of the rotational speed of the magnetic field at which torque oscillations are observed.

The electric machine can be synchronous or asynchronous.

• la figure 1 illustre les principaux éléments d'un système de commande selon l'invention, et
• la figure 2 illustre les principales étapes d'un procédé de commande selon l'invention.

Other objects, features and advantages will appear on reading the following description given solely as a non-limitative example and with reference to the appended drawings in which:

• the figure 1 illustrates the main elements of a control system according to the invention, and
• the figure 2 illustrates the main steps of a control method according to the invention.

The control system 1, illustrated by the figure 1 of an electric machine 2 comprises means 3 for determining current values relative to each of the phases of the electric machine in the frame (d, q, f) of Park as a function of the torque request of the conductor C ^ref .

The control system 1 comprises a regulation means 4 of the currents in the phases of the electric machine. The regulating means 4 determines supply voltages Vd, Vq, Vf of each of the phases of the electric machine according to the current instructions received at the input.

${\mathrm{I}}_{\mathrm{q}}^{\mathrm{att}},$

${\mathrm{I}}_{\mathrm{f}}^{\mathrm{att}}$

des oscillations de couple relatifs à chaque phase.The control system 1 also comprises a torque oscillation correction means 5 receiving at input the supply voltages V _d , V _q , V _f of each of the phases, measurements of the currents of each phase I _d , I _q , I _f as well as a measurement of the rotational speed ω _r of the magnetic field. The means 5 for correcting torque oscillations emit attenuation currents at the output ${\mathrm{I}}_{\mathrm{d}}^{\mathrm{att}},$

${\mathrm{I}}_{\mathrm{q}}^{\mathrm{att}},$

${\mathrm{I}}_{\mathrm{f}}^{\mathrm{att}}$

torque oscillations relative to each phase.

A first subtractor 6 performs the subtraction between the current setpoint of the phase d and the corresponding attenuation current. It outputs a final current setpoint relative to phase d.

A second subtractor 7 and a third subtractor 8 perform similar subtractions on the relative values respectively to the phase q and the phase f.

Thus, when the system is started, the current setpoint of each phase is transmitted without modification to the regulation means 4 of the currents. However, as soon as measurements of the currents of each phase I _d , I _q , I _f and a measurement of the rotational speed ω _r of the magnetic field are available, the current instructions transmitted to the current regulation means 4 are the final current setpoints, thus making it possible to reduce or even eliminate the torque oscillations.

The control method of an electric machine makes it possible to provide a dynamic correction of the current setpoints so as to reduce the amplitude of the torque oscillations.

On the figure 2 it can be seen that the process starts with a step 9 of calculating the powers of each phase, applying the following equations: $$\{\begin{array}{cc}{\mathrm{P}}_{\mathrm{d}}& ={\mathrm{V}}_{\mathrm{d}}{\mathrm{I}}_{\mathrm{d}}-{\mathrm{R}}_{\mathrm{s}}{\mathrm{I}}_{\mathrm{d}}^{\mathrm{2}}\\ {\mathrm{P}}_{\mathrm{q}}& ={\mathrm{V}}_{\mathrm{q}}{\mathrm{I}}_{\mathrm{q}}-{\mathrm{R}}_{\mathrm{s}}{\mathrm{I}}_{\mathrm{q}}^{\mathrm{2}}\\ {\mathrm{P}}_{\mathrm{f}}& ={\mathrm{V}}_{\mathrm{f}}{\mathrm{I}}_{\mathrm{f}}-{\mathrm{R}}_{\mathrm{<figure-callout\; id="2"\; label="f\; I\; f"\; filenames="imgf0001.png"\; state="\{\{state\}\}">f\; </figure-callout>}}{\mathrm{I}}_{\mathrm{f}}^{}{\mathrm{}}_{\mathrm{2}}^{}\end{array}$$

• P_d la puissance de la phase d,
• P_q la puissance de la phase q, et
• P_f la puissance de la phase f.

With

• P _d the power of phase d,
• P _q the power of phase q, and
• P _f the power of phase f.

During a second step 10, it is determined whether the rotational speed ω _r of the magnetic field exceeds a threshold value. The threshold value is determined based on previous tests, during which couples oscillations are observed. The threshold value is then set to a value equal to the rotational speed of the magnetic field at which the torque oscillations have been observed. It is recalled that speed of rotation and frequency of rotation are directly related. If this is the case, bandpass filtering of each power signal is applied to extract only the relevant frequencies. The band pass filter is configured with a low cutoff frequency lower than the rotation frequency of the magnetic field at which the oscillations are observed and a high cutoff frequency greater than the rotation frequency of the magnetic field at which the oscillations are observed.

la puissance de la phase d après filtrage, ${\mathrm{P}}_{\mathrm{q}}^{\mathrm{filt}}$

la puissance de la phase q après filtrage, et ${\mathrm{P}}_{\mathrm{f}}^{\mathrm{filt}}$

la puissance de la phase f après filtrage.We then obtain ${\mathrm{P}}_{\mathrm{d}}^{\mathrm{filt}}$

the power of the phase after filtering, ${\mathrm{P}}_{\mathrm{q}}^{\mathrm{filt}}$

the power of the phase q after filtering, and ${\mathrm{P}}_{\mathrm{f}}^{\mathrm{filt}}$

the power of the phase f after filtering.

During a third step 11, each power is multiplied after filtering by calibrated gains to obtain the attenuation currents for each phase. The following equations are used to determine these currents: $$\{\begin{array}{cc}{\mathrm{I}}_{\mathrm{d}}^{\mathrm{att}}& ={\mathrm{\alpha }}_{\mathrm{d}}{\mathrm{P}}_{\mathrm{d}}^{\mathrm{filt}}\\ {\mathrm{I}}_{\mathrm{q}}^{\mathrm{att}}& ={\mathrm{\alpha }}_{\mathrm{q}}{\mathrm{P}}_{\mathrm{q}}^{\mathrm{filt}}\\ {\mathrm{I}}_{\mathrm{f}}^{\mathrm{att}}& ={\mathrm{\alpha }}_{\mathrm{f}}{\mathrm{P}}_{\mathrm{f}}^{\mathrm{filt}}\end{array}$$

• ${\mathrm{I}}_{\mathrm{d}}^{\mathrm{att}}:$
  
  courant d'atténuation relatif à la phase d
• ${\mathrm{I}}_{\mathrm{q}}^{\mathrm{att}}:$
  
  courant d'atténuation relatif à la phase q
• ${\mathrm{I}}_{\mathrm{f}}^{\mathrm{att}}:$
  
  courant d'atténuation relatif au rotor f
• α_d : gain calibrable relatif à la phase d
• α_q : gain calibrable relatif à la phase q
• α_f : gain calibrable relatif au rotor f

With

• ${\mathrm{I}}_{\mathrm{d}}^{\mathrm{att}}:$
  
  attenuation current relative to the phase d
• ${\mathrm{I}}_{\mathrm{q}}^{\mathrm{att}}:$
  
  attenuation current relative to the phase q
• ${\mathrm{I}}_{\mathrm{f}}^{\mathrm{att}}:$
  
  attenuation current relative to the rotor f
• α _d : calibratable gain relative to the phase d
• α _q : calibrated gain relative to the phase q
• α _f : calibratable gain relative to the rotor f

During a fourth step 12, the attenuation currents relative to each phase are subtracted from the current setpoints relative to the corresponding phases and determined according to the torque request of the conductor. The following equations make it possible to determine the final flow instructions resulting from the subtraction: $$\{\begin{array}{cc}{\mathrm{I}}_{\mathrm{d}}^{\mathrm{end}}& ={\mathrm{I}}_{\mathrm{d}}^{\mathrm{ref}}-{\mathrm{I}}_{\mathrm{d}}^{\mathrm{att}}\\ {\mathrm{I}}_{\mathrm{q}}^{\mathrm{end}}& ={\mathrm{I}}_{\mathrm{q}}^{\mathrm{ref}}-{\mathrm{I}}_{\mathrm{q}}^{\mathrm{att}}\\ {\mathrm{I}}_{\mathrm{f}}^{\mathrm{end}}& ={\mathrm{I}}_{\mathrm{f}}^{\mathrm{ref}}-{\mathrm{I}}_{\mathrm{f}}^{\mathrm{att}}\end{array}$$

• ${\mathrm{I}}_{\mathrm{d}}^{\mathrm{fin}}:$
  
  consigne de courant finale relative à la phase d
• ${\mathrm{I}}_{\mathrm{q}}^{\mathrm{fin}}:$
  
  consigne de courant finale relative à la phase q
• ${\mathrm{I}}_{\mathrm{f}}^{\mathrm{fin}}:$
  
  consigne de courant finale relative au rotor f
• ${\mathrm{I}}_{\mathrm{d}}^{\mathrm{ref}}:$
  
  consigne de courant relative à la phase d
• ${\mathrm{I}}_{\mathrm{q}}^{\mathrm{ref}}:$
  
  consigne de courant relative à la phase q
• ${\mathrm{I}}_{\mathrm{f}}^{\mathrm{ref}}:$
  
  consigne de courant relative au rotor f

With

• ${\mathrm{I}}_{\mathrm{d}}^{\mathrm{end}}:$
  
  final current setpoint relative to the phase d
• ${\mathrm{I}}_{\mathrm{q}}^{\mathrm{end}}:$
  
  final current setpoint relative to the phase q
• ${\mathrm{I}}_{\mathrm{f}}^{\mathrm{end}}:$
  
  final current reference relative to the rotor f
• ${\mathrm{I}}_{\mathrm{d}}^{\mathrm{ref}}:$
  
  current setpoint relative to the phase d
• ${\mathrm{I}}_{\mathrm{q}}^{\mathrm{ref}}:$
  
  current setpoint relative to the phase q
• ${\mathrm{I}}_{\mathrm{f}}^{\mathrm{ref}}:$
  
  current reference relative to the rotor f

The final current instructions are then sent to the control means (4) of the electric machine during a fifth step 13.

It should be noted that the system and the control method of the electrical machine for reducing the torque oscillations described above can be applied to all synchronous or asynchronous electrical machines.

Claims (8)

1. Method for controlling a three-phase electric machine (2) of a motor vehicle powered by chopped voltages and comprising a step of determination of current setpoints for each phase of the electric machine (2) as a function of a torque request from the driver, and a step of determination of the voltages of each phase of the electric machine (2) as a function of the current setpoints for each phase, characterized in that it comprises the following steps during which:

   the powers of each phase of the electric machine are determined, expressed in the Park reference frame,

   a determination is made as to whether a measurement of the speed of rotation of the magnetic field in the electric machine (2) exceeds a threshold value, and, if it does, a bandpass filtering of the powers of each phase of the electric machine (2) is performed,

   each power after filtering is multiplied by gains that can be calibrated to obtain attenuation currents relative to each phase,

   final current setpoints are determined by subtracting the attenuation currents relative to each phase from the current setpoints of the corresponding phases, and

   power supply voltage setpoints for the phases of the electric machine are determined as a function of the final current setpoints.
2. Method according to the preceding claim, in which the bandpass filtering is performed for a low cut-off frequency below the frequency of rotation of the magnetic field at which the oscillations are observed and a high cut-off frequency above the frequency of rotation of the magnetic field at which the oscillations are observed.
3. Method according to either one of the preceding claims, in which the electric machine is synchronous or asynchronous.
4. Method according to any one of the preceding claims, in which the rotation speed threshold of the magnetic field is determined as a function of the speed of rotation of the magnetic field at which torque oscillations are observed.
5. System for controlling a three-phase electric machine (2) of a motor vehicle powered by chopped voltages, comprising a means (3) for determining current setpoints of each phase of the electric machine as a function of a torque request from the driver,
   and a means (4) for regulating the currents capable of determining voltages of each phase of the electric machine as a function of the current setpoints for each phase, characterized in that it comprises a means (5) for correcting the torque oscillations, capable of determining the powers of each phase of the electric machine expressed in the Park reference frame, the correction means (5) being also capable of determining whether a measurement of the speed of rotation of the magnetic field in the electric machine exceeds a threshold value, and of performing a bandpass filtering of the powers of each phase of the electric machine, and for determining attenuation currents relative to each phase as a function of the powers after filtering, and subtractors (6, 7, 8) capable of subtracting the attenuation currents relative to each phase from the current setpoints relative to the corresponding phases in order to obtain final current setpoints, and capable of sending the final current setpoints to the regulation means (4) of the electric machine.
6. System according to Claim 5, in which the bandpass filtering is performed for a low cut-off frequency below the frequency of rotation of the magnetic field at which the oscillations are observed and a high cut-off frequency above the frequency of rotation of the magnetic field at which the oscillations are observed.
7. System according to either one of Claims 5 and 6, in which the rotation speed threshold of the magnetic field is determined as a function of the speed of rotation of the magnetic field at which torque oscillations are observed.
8. System according to any one of Claims 5 to 7, in which the electric machine is synchronous or asynchronous.

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